Method of making absorbent dental point



Aug. 12, 1958 J. N. ,MASCI EI'AL 2,846;927

METHOD OF MAKING ABSORBENT DENTAL POINT Filed Oct. 25, 1954 v I INVE TO 3:

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METHOD OF MAKENG 'ABSORBENT DENTAL POINT Joseph N. Masci, Metuehen, N. l, and William H. Ashton, Fhiladelphia, Pa, assignors to Johnson & Johnson, a corporation of New .lersey Application Gctober 25, M54, Serial No. 464,490 4 Claims. (Cl. 93-4) This invention relates to a product for dental use and, in particular, to absorbent dental points.

Absorbent dental points are elongated fibrous sticks or swabs employed in the profession to treat the root canal of the tooth. In general therapy in this field, absorbent dental points are used to dry out the root canal, apply medicament to it, or to isolate and determine which bacteria are present in this area. There are many genuses of bacteria which cause trouble in the area. They include common types such as Gamma streptococci, yeasts, Staph. albus, Alpha streptococci, Bac. acidophilus, Staph. aureus, Bac. subtilis, Staph. citreus, Baa. 0011'. According to dental authorities, a high percentage of single organism infections of root canals are due to the first four groups mentioned above.

When it is desired to apply medication, the absorbent point is immersed in a solution of and absorbs the medicament desired, and is then inserted into the tooth where it releases a part of the medicament into the part of the tooth undergoing treatment.

It is very important to conduct dental therapy relating to the root canal with as high a degree of antisepsis as possible. Absorbent points now available for this work are supplied in a sterile package. There may be from 50 to 200 individual points per package. Ordinarily, the dentist uses from 5 to points per treatment. Under these circumstances, the points are sterile the first time the package is opened, but the unused bulk of points in the package become contaminated with air-borne bacteria or by bacteria transferred from the instruments introduced into the package.

Since the organisms are so common and troublesome, care must be exercised to avoid their introduction to the dental point. One solution to the problem has been the advent of a small molten metal sterilizer. The dentist selects a point and holds it in the molten metal for about ten seconds, and then introduces it immediately into a pulp cavity or root canal, or into the medicament solution, and then into the tooth. The alloys used are mixtures of bismuth, lead, and tin, which are available in melting points ranging from 320 F. to 380 F., the unit being thermo-regulated at least 50 F. above the melting point of the particular alloy.

In view of the use to which these points are put, there are several important properties which they should possess, and the method of manufacture should be sov designed as to impart these properties to the final product. In the first place, the method should impart wicking action so that the points imbibe exudates present in the root canal or pulp cavity, and are also capable of absorbing medicaments and releasing them in the tooth cavity.

In the second place, the points should be reasonably stiff so as to permit insertion into a small opening, and yet they should be flexible enough to follow tortuous routes in atypical root canals or pulp cavities.

In the third place, the points should be made to have a relatively high degree of crosswise and longitudinal strength, particularly when wet, to prevent them from 2,846,927 Patented Aug. 12, 1958 a; breaking oif or being torn apart when removed from the canal.

In the fourth place, the points should be free from binders which react with or impede the effectiveness of medicaments or lower the absorbency of the points.

Finally, the points should be made to withstand temperatures in the range 370- to 450 F. for at least ten seconds in molten metal sterilizers without deleterious effect on any of the preceding properties.

Absorbent dental points which have enjoyed the widest usage have been made from a thin bibulous paper impregnated with gum tragacanth and sodium borophosphate as a binder. They have relatively poor wet strength and become embrittled and, in many cases, charred when subjected to molten metal sterilization. In some cases, when using the conventional points, the tip of the point would break off during insertion or removal, leaving the tip in the bottom of the root canal. Removal was extremely diflicult. Further, the tragacanth-borophosphate binder is incompatible with and interferes with the use of some types of dental medicaments.

According to the invention, there is produced an absorbent dental point which combines all the desired advantageous properties set forth above. This method involves plasticizing or lubricating a sheet of hemp fiber paper with a suitable liquid lubricating agent, rolling the sheet into a tightly compacted point, and then drying the product. The method may be conveniently understood by reference to the attached drawing.

Figure 1' is a view of a sheet of the particular paper employed according to the invention in manufacturing absorbent dental points.

Figure 2 is a view of the completed point.

Reference number 10 indicates the blank or stock which is a sheet of paper having triangular shape with two sides 11 and 12 of substantially equal length and a third side 15 having shorter length. Apex 16 is a corner of the sheet opposite side 15. It will be noted that fibers 1'7, constituting sheet 10, are substantially oriented in the direction of the long axis a-a of the blank.

In manufacture of the absorbent dental point, the blank 10 is first moistened with a suitable lubricant, described more fully below, and then rolled on axis a-a beginning, for example, at corner 20. The rolling is continued until finally the entire sheet has been tightly wound, still retaining the same axis a-a in the completed point 21. The wound product is then dried.

The fibrous sheet selected for manufacture of absorbent dental points according to the invention is made of hemp. Hemp is made of relatively long and strong fibers. Using the lubricant according to the invention method, the hemp fibers compact and reinforce themselves and thereby make possible the production of a finished dental point which is strong in the transverse as well as the longitudinal direction, without resorting to use of the conventional binders. The fibers in the hemp sheet are preferably substantially oriented in a direction parallel to the axis of the point, thereby providing marked strength, particularly in the all-important longitudinal direction and even when wet, to prevent breaking of the thin tip of the point. The paper is of sufiicient thickness to afford a product having desired bulk while not being too large to prevent its insertion into the tooth cavity. Paper having a thickness of 0.001 in. made on a cylinder type unit is suitable. Paper so made has fiber orientation much the same as a cotton card web, and this feature is desirable from the standpoint just mentioned.

The preferred lubricating agent for the purpose of the invention method is water. It has been found that water lubricates the hemp fibers to the degree that they intermingle and intermesh with each other to yield a strong and durable product having the above sought-for characteristics. Lubricant is used in amount sufficient to lubricate and plasticize the fibers so that, in the method of manufacture described, the product assumes the desired properties. Generally, at least about 50% lubricant based on the weight of the paper is preferred due to the appreciable compression applied to the product during manufacture. Excess lubricant will be expressed, and, accordingly, there is no particular advantage in using amount of lubricant greater than 150% based on the weight of the paper.

If it is desired to impart to the dental point a greater degree of stifiness, polyvinyl alcohol may be added to the water lubricant and, by use of this aqueous polyvinyl alcohol solution, to the absorbent dental point. Polyvinyl alcohol is supplied commercially in a variety of types and by a variety of manufacturers. Any of these types which possess sufiiciently high water solubility, as for example, those recommended for use in sizing solutions, etc., may be used for the purposes of the present invention. One type having a viscosity of 45 to 55 centipoises, as determined by the Hoeppler falling ball method (determined in a 4% aqueous solution at 20 C.), about 98100% hydrolyzed (from vinyl acetate), and having a pH of from 6 to 8, may be used as a bonding agent in the present invention. Another suitable type is that sold by the same manufacturer having viscosities of 35 to 45 by the Hoeppler method, 8689% hydrolyzed, and having a pH in the range of 6 to 8. The percentage concentration of polyvinyl alcohol in the lubricant solution and the amount of such solution applied to the hemp paper may be varied in direct proportion to the degree of stiffness desired to be imparted to the dental point. In general, with greater concentrations of polyvinyl alcohol, lesser amounts of lubricant solution need be added; and, conversely, with greater pick-up of solution by the paper, lower concentrations of alcohol should be employed if it is desired to limit the net amount of polyvinyl alcohol added to each point. Suitable ranges of polyvinyl alcohol, however, may be found within the range 0.1% to saturation. Pick-up of lubricant solution may be within the range described above for water, the concentration and pick-up preferably being coordinated to provide a prodnot which contains polyvinyl alcohol in the range 0.25 to 2.0%.

Following is an example presented as illustrating, rather than limiting the invention.

Example Blank-s were cut from a sheet of manila hemp paper having a thickness of 0.001 in. made on a cylinder type paper-making machine. The blanks had substantially the shape illustrated in Fig. 1 with sides 11 and 12 one and one-eighth inch in length, and side 15 one inch in length. The average dry weight of the blanks was 0.0044 gram. The fibers in the paper were oriented parallel to axis a-a as evidenced by tearing the sheet in longitudinal and transverse directions. A number of the blanks were moistened with water and rolled by hand into the shape described in Fig. 2. The average moist weight of the points was 0.0094 gram, indicating 113% water pick-up dry basis. Another group of blanks were moistened with a 1.0% by weight solution of polyvinyl alcohol having viscosity of 45-55 centipoises, 97.998.7% hydrolysis and pH 6-8. These blanks were rolled into points, as described above, and as described in Fig. 2. The moist weight of 23 of the latter group of points was 0.21501 gram, indicating a total lubricant content of 0.1140 gram, a lubricant pick-up of 113% based on the dry weight of the blanks and a polyvinyl alcohol content of 1.1% dry basis. Water was removed from both groups of points to produce a substantially dry product. The water-lubricated points and the polyvinyl alcohol-lubricated points were tested in comparison with conventional absorbent dental points made from bibulous paper bonded with tragacanthborophosphate binder by immersing each in a molten metal sterilizing bath at about 440 F. for ten seconds. The conventional points became too friable and brittle in the course of sterilization to be satisfactory for use. The latter exhibited an extremely undesirable tendency to break oil when inserted into the root canal. The water and polyvinyl alcohol-lubricated hemp fiber points were found to be clinically satisfactory for removing moisture from the root canal, and for the application of fluid medicaments.

Many modifications and equivalents within the spirit and scope of the invention will now be apparent in the light of the foregoing specific description. Accordingly, it is intended to include such modifications and equivalents within the scope of protection sought.

The claims are:

1. The method of making an absorbent dental point which comprises moistening a blank of manila hemp paper having substantially triangular shape and fibers oriented substantially in the direction from one angle thereof toward the middle of the opposite side, With an aqueous lubricant of the group consisting of water and an aqueous solution of polyvinyl alcohol, rolling said blank into a point by starting at one corner and tightly winding until the entire sheet has been tightly wound, the fibers being oriented substantially in the direction of the axis of said point, and drying said point.

2. The process according to claim 1 in which the amount of lubricant used is at least about 50% based on the Weight of the dry paper.

3. The process according to claim 2 in which the lubricant is Water.

4. The process according to claim 2 in which the lubricant is aqueous solution of polyvinyl alcohol.

References Cited in the file of this patent UNITED STATES PATENTS 1,312,120 Hurtt Aug. 5, 1919 1,649,508 Carmichael Nov. 15, 1927 1,757,595 Siegel May 6, 1930 2,218,525 Decker Oct. 22, 1940 2,251,296 Shipp Aug. 5, 1941 2,275,578 Wood Mar. 10, 1942 2,546,618 Talet Mar. 27, 1951 OTHER REFERENCES Filling the Root Canal, A. B. Crane, Dental Cosmos, vol. LXVII, July 1926, pages 709-713. (Copy in Div. 55.)

Materials Used in Root-Canal Technique in Dental Practice, by W. K. Conrad, Dental Cosmos, vol. LXXVI, March 1934, pages 311 to 315. (Copy in Div. 55.)

Dictionary of Paper, American Paper and Pulp Association, New York, N. Y. (1951), Geo. Banto Publishing Co., Menasha, Wisconsin, pages 200 and 235 and 236. (Copy in Div. 67.) 

1. THE METHOD OF MAKING AN ABSORBENT DENTAL POINT WHICH COMPRISES MOISTENING A BLANK OF MANILA HEMP PAPER HAVING SUBSTANTIALLY TRIANGULAR SHAPE AND FIBERS ORIENTED SUBSTANTIALLY IN THE DIRECTION FROM ONE ANGLE THEREOF TOWARD THE MIDDLE OF THE OPPOSITE SIDE, WITH AN AQUEOUS LUBRICANT OF THE GROUP CONSISTING OF WATER AND AN AQUEOUS SOLUTION OF POLYVINYL ALCOHHOL, ROLLING SAID BLANK INTO A POINT BY STARTING AT ONE CORNER AND TIGHTLY WINDING UNTIL THE ENTIRE SHEET HAS BEEN TIGHTLY WOUND, THE FIBERS BEING ORIENTED SUBSTANTIALLY IN THE DIRECTION OF THE AXIS OF SAID POINT, AND DRYING SAID POINT. 